The traditions from biblical times are much different than what is acceptable today, so the age of marriage might make you look upon the patriarchs differently. I believe Rebecca was very young when her family gave her away, and Isaac took her to be his wife; she had a nurse. However, she was old enough to understand, connect words and fill a trough for the camels. Her age at marriage could be why it was nearly 20 years later that they had Esau and Jacob. The Bible says she was barren, and Isaac prayed for God to bless them with children. It was God who made them wait to continue the promise. He was going to answer his prayer anyway but may have been waiting for him to ask. What are you waiting for? God may have plans to answer your prayers but is probably waiting for you to ask. Stop now and talk to God about what’s on your mind; he’s waiting to hear from you.
And Isaac was forty years old when he took Rebekah to wife, the daughter of Bethuel the Syrian of Padanaram, the sister to Laban the Syrian. And Isaac intreated the LORD for his wife, because she was barren: and the LORD was intreated of him, and Rebekah his wife conceived. Genesis 25:20-21